The present invention relates to a liposome composition. More particularly, the present invention relates to a liposome composition in which a drug is retained in a stable condition within liposomes and which is conducive to a sustained therapeutic efficacy or a better delivery of the drug to a target organ.
In using liposomes as carriers for drugs, it is essential to improvement of therapeutic effects to ensure that the drugs are retained in as stable a condition as possible within the liposomes. Heretofore, much research has been undertaken into the stability of liposomes but little attention has been paid to the relationship between the stability of liposomes and the osmotic pressure in preparation. As mentioned in "Saibo Kogaku" (Cell Engineering)2, 1136 (1983), for instance, it has been claimed that "as a rule, it is essential that the solution in preparation is isotonic with the solution used later as the disperse medium". On the other hand, no attention has been paid to the case in which the solution in the preparation of liposomes is lower than the osmotic pressure used later as the dispersion medium.